1. Field of the Invention
This invention relates to an antibacterial rockwool growth medium for hydroponics used for hydroponic growth of rice, flowers and ornamental plants, fruitage, etc.
2. Description of the Related Art
In hydroponics, measures against bacteria in which a nutrient solution primarily serves as a medium include addition of agricultural chemicals, disinfection by addition of hypochlorous acid, disinfection by antibacterial metal ion such as eluted silver or copper, high temperature sterilization and disinfection by ozone. In the disinfection by the eluted metal ion, a metal ion is eluted in a nutrient solution to displace a sulfhydryl group (—SH) possessed by bacteria, whereby the bacteria is deactivated. Furthermore, when added into the nutrient solution of hydroponics, agricultural chemical, chlorine, or ion such as silver or copper has a quick-acting property and is accordingly effective. However, there is a possibility that plant roots may be damaged by chemical injury. Moreover, since the effect of the foregoing method is not persistent, an antibacterial or bactericidal component in the nutrient solution needs to be continuously controlled. In the high temperature sterilization or ozonic disinfection, an aseptic condition can be maintained for a short period of time after the treatment, but almost no disinfection effect can be achieved near the plant root when bacteria invade the nutrient solutions during subsequent circulation.
A rockwool base used for the hydroponics is sterilized at the time of completion of manufacture since it is sintered at 200° C. to 300° C. at a final manufacturing step. Accordingly, once invading the rockwool base, bacteria rapidly propagate themselves such that the rockwool base is contaminated by the bacteria. Replanting is impossible in the use of the contaminated rockwool culture medium. Thus, a plant growing method in which disinfection can reliably take place near the plant root has been desired.